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sched/core: Optimize SCHED_SMT

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Avoid pointless SCHED_SMT code when running on !SMT hardware.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2016-05-09 10:38:41 +02:00 committed by Ingo Molnar
parent 10e2f1acd0
commit 1b568f0aab
3 changed files with 43 additions and 7 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

19
kernel/sched/core.c
View file

@ -7412,6 +7412,22 @@ int sched_cpu_dying(unsigned int cpu)
}
#endif
#ifdef CONFIG_SCHED_SMT
DEFINE_STATIC_KEY_FALSE(sched_smt_present);
static void sched_init_smt(void)
{
/*
* We've enumerated all CPUs and will assume that if any CPU
* has SMT siblings, CPU0 will too.
*/
if (cpumask_weight(cpu_smt_mask(0)) > 1)
static_branch_enable(&sched_smt_present);
}
#else
static inline void sched_init_smt(void) { }
#endif
void __init sched_init_smp(void)
{
cpumask_var_t non_isolated_cpus;
@ -7441,6 +7457,9 @@ void __init sched_init_smp(void)
init_sched_rt_class();
init_sched_dl_class();
sched_init_smt();
sched_smp_initialized = true;
}

8
kernel/sched/fair.c
View file

@ -5357,7 +5357,7 @@ static inline bool test_idle_cores(int cpu, bool def)
* Since SMT siblings share all cache levels, inspecting this limited remote
* state should be fairly cheap.
*/
void update_idle_core(struct rq *rq)
void __update_idle_core(struct rq *rq)
{
int core = cpu_of(rq);
int cpu;
@ -5389,6 +5389,9 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int
struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
int core, cpu, wrap;
if (!static_branch_likely(&sched_smt_present))
return -1;
if (!test_idle_cores(target, false))
return -1;
@ -5422,6 +5425,9 @@ static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int t
{
int cpu;
if (!static_branch_likely(&sched_smt_present))
return -1;
for_each_cpu(cpu, cpu_smt_mask(target)) {
if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
continue;

23
kernel/sched/sched.h
View file

@ -36,12 +36,6 @@ extern void cpu_load_update_active(struct rq *this_rq);
static inline void cpu_load_update_active(struct rq *this_rq) { }
#endif
#ifdef CONFIG_SCHED_SMT
extern void update_idle_core(struct rq *rq);
#else
static inline void update_idle_core(struct rq *rq) { }
#endif
/*
* Helpers for converting nanosecond timing to jiffy resolution
*/
@ -730,6 +724,23 @@ static inline int cpu_of(struct rq *rq)
#endif
}
#ifdef CONFIG_SCHED_SMT
extern struct static_key_false sched_smt_present;
extern void __update_idle_core(struct rq *rq);
static inline void update_idle_core(struct rq *rq)
{
if (static_branch_unlikely(&sched_smt_present))
__update_idle_core(rq);
}
#else
static inline void update_idle_core(struct rq *rq) { }
#endif
DECLARE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
#define cpu_rq(cpu) (&per_cpu(runqueues, (cpu)))